Alleged screenshots taken by developer Steven
Troughton-Smith suggest apps may be optimized for the
5.5-inch iPhone's bigger screen with a new split-screen
view.

When you tilt the 5.5-inch iPhone to landscape mode, iOS 8 will
automatically adapt to take advantage of the phone's larger
screen. As 9to5Mac notes, this means you'd be able to see more
information than usual when using the phone in landscape mode.

For example, when using the Contacts app in landscape mode, the
phone could display specific information pertaining to an
individual person alongside your full list of phone numbers, as
shown in the screenshot below.

Apple's larger iPhone may
be able to display apps in a split-screen
mode.9to5Mac

The same goes for the Calendar app, too. Notice how the
screenshot below displays the month view alongside a specific
day.

Apple's larger iPhone may
be able to display apps in a split-screen
mode.9to5Mac

When tilting the phone to landscape mode in the Game Center, you
can look at your list of friends while also viewing individual
statistics for one person.

Apple's larger iPhone may
be able to display apps in a split-screen
mode.9to5Mac

It's a small feature, but it's one that could make the larger
iPhone 6's screen more useful. It also further suggests that
Apple is planning to tweak its larger-screened devices for more
productive use cases. Back in June, developers began spotting
code in iOS 8 that suggested a split-screen interface for apps
could be coming to the iPad soon. Certain Android phones like
Samsung's Galaxy S5 and LG's G3 already allow you to do this, but
this would be the first time we're seeing split-screen
functionality coming to iOS devices.